I. Field
The present disclosure relates generally to wireless communications, and more specifically to techniques for signal acquisition and transmission in a wireless communication system.
II. Background
Wireless communication systems are widely deployed to provide various communication services; for instance, voice, video, packet data, broadcast, and messaging services may be provided via such wireless communication systems. These systems may be multiple-access systems that are capable of supporting communication for multiple terminals by sharing available system resources. Examples of such multiple-access systems include Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, and Orthogonal Frequency Division Multiple Access (OFDMA) systems.
Wireless communication systems often utilize frequency division duplexing (FDD) for data transmission between base stations and wireless terminals on the forward and reverse links, wherein separate channels are used for the forward and reverse links such that a wireless terminal may simultaneously receive data on a forward link (FL) channel and transmit data on a reverse link (RL) channel. The forward link (or “downlink”) refers to the communication link from the base stations to one or more terminals, while the reverse link (or “uplink”) refers to the communication link from a terminal to one or more base stations.
Terminals designed for operation in a FDD system are able to receive and transmit at the same time by using a duplexer, which assigns FL communications and RL communications to different frequency bands to allow simultaneous FL and RL communication. To support terminals that are not capable of receiving and transmitting at the same time, a FDD system can additionally provide half-duplex communication by dividing frames on the forward and reverse links into half-duplex interlaces such that a base station and a terminal communicating on a half-duplex interlace can alternate between FL and RL transmission. Half-duplex interlaces are typically created by grouping forward and reverse link frames into superframes and dividing frames in each superframe among the half-duplex interlaces such that all interlaces are allocated an equal number of frames in each superframe and that a given frame position in a superframe always corresponds to a particular communication link (i.e., the forward link or the reverse link) for a given interlace.
A terminal in a wireless communication system may not know which base stations, if any, near its vicinity are transmitting. Furthermore, in a system where base stations operate asynchronously, the terminal may not know the timing information necessary for communication with a particular base station. Thus, a terminal can perform signal acquisition on the forward link to detect for transmissions from base stations in the system and to synchronize to the timing and frequency of each detected base stations of interest. A base station can transmit acquisition pilots or other signals to aid in signal acquisition and allow a terminal to detect the base station. However, in a FDD system utilizing half-duplex communication where base stations operate asynchronously, some or all of the acquisition pilots transmitted by a base station may be transmitted exclusively during RL transmissions of a terminal operating on a single half-duplex interlace. As a result, terminals operating on a single-half duplex interlace may not be able to detect asynchronous base stations in the system, which can result in a decrease in system efficiency.